Gas analyzer



July 30, 1946. A. P. SULLWAN GAS ANALYZER Filed Jan. 22, 1940 "w ENTORAll/4N f. JULLlV/l/V avg ATTORNEY Patented July 30, 1946 GAS ANALYZERAlan P. Sullivan, Elizabeth, N. J., assignor to Cities Service OilCompany, New York, N. Y., a corporation of Pennsylvania ApplicationJanuary 22, 1940, Serial No. 314,899

3 Claims. 1

This invention relates to gas analyzers, and more particularly to anapparatus adapted to give accurate and sensitive measurements of theoxygen and combustible content of a gas in either low percentages orrelatively high percentages of oxygen and combustibles.

The invention is particularly adapted for the analyses of exhaust gases,such as domestic and industrial furnace exhaust gases, Diesel andgasoline engine exhaust gases; and for other types of gases, such asmine gases and atmospheres in which the percentage of the combustiblesand oxygen is not very large.

The apparatus of this invention is an improvement on and a continuationin part of the apparatus described in the Patent No. 2,273,981, issuedFebruary 24, 1942, to John D. Morgan and Alan P. Sullivan.

In the apparatus of the above patent, the gas to be analyzed is ignitedin a combustion chamber by means of a platinum or platinum-alloycatalyst wire, which forms one leg of a Wheatstone bridge. The heat ofcombustion of the gas raises the temperature of the catalytic leg of theWheatstone bridge, thus increasing its resistance proportionally to theamount of combustibles or oxygen in the gas. This change in the amountof resistance is indicated on a galvanometer connected across theWheatstone bridge circuit.

The most efficient operatin temperature range for the catalyst wire in agas analyzer of this type has been found to be from l400 to 1600 F.

If a platinum or platinum-alloy catalyst wire is operated below 1400 F.for the ignition of exhaust gases, such as exhaust gases from aninternal combustion engine which contain partial oxidation products ofhydrocarbons, the catalyst will lose its activity in a very short timedue to poisoning. In other types of gases burned below 1400" F. theignition is irregular and not dependable, due to incomplete combustionand formation of partial oxidation products.

The loss of activity of the catalyst wire due to poisoning above 1400 F.has been eliminated by the manner of assemblage and treatment of thecatalyst as described in Patent 2,273,981.

When a platinum or platinum-alloy catalyst wire i operated above 1600F., its life is considerably shortened due to the vaporization of thewire.

Such an apparatus, as described in the Patent No. 2,273,981, has beenfound to give accurate and sensitive analyses of a gas in the range ofthe percentage of oxygen and combustibles for which it was designed; butit is not suitably adapted to 2. give sensitive analyses of gases whoseoxygen and combustible content varies over a wider percentage range.This lack of sensitivity of a single range apparatus for analyses inwide percentage ranges results from the necessity of the operation ofthe catalyst wire in a temperature range of 1400" to 1600 F. in order toinsure long life, accuracy, and sensitivity to the catalyst wire.

The primary object of the invention is to provide a simple, accurate,and sensitive gas analyzer which can be used for measuring the oxygenand combustible content of gases in either a range of high or lowpercentages of oxygen and combustibles; and yet maintaining thetemperature of the catalyst wire in the most effioient opcratingtemperature range of 1400 to 1600 F.

Another object of the invention is to provide a gas analyzing apparatuswhich is adapted to be used as an indicating means for adjustingdomestic furnaces, industrial furnaces, Diesel engines, and gasolineengines to the highest degree of opcrating efficiency.

The present invention is particularly adapted for analyses of gasesexhausted from steam boiler furnaces, metallurgical furnaces, andinternal combustion engines, particularly gasoline engines and Dieselengines. The exhaust gases from a gasoline engine rarely have freeoxygen content, but all the other gases from the diiTerent types offurnaces and engines usually have both oxygen as well as combustibleconstituents. The apparatus is therefore well adapted for analyzinggases having both oxygen and combustible content, as the sample takeninto the apparatus is divided and each part analyzed simultaneously.

The apparatus is so designed that a very short lag exists between thetime that the sample is taken into the apparatus and the time that theanalyses are determined. Therefore, this apparatus may be used foraccurately controlling combustion in all types of furnaces and internalcombustion engines.

Fundamentally, the apparatus of this invention provides for thesimultaneous measurements of the combustible content, the oxygencontent, and the temperature of the gas to be analyzed; keeping thecatalyst wire temperature in the range of 1400 to 1600 F. andnevertheless obtaining sensitive measurements regardless of the amountof oxygen and combustibles in the gas.

In the operation of the gas analyzer, the gas sample is divided into twoparts. Hydrogen is added to one part, and the mixture of hydrogen andsample gas is conveyed to the oxygen analyzing chamber to be analyzed todetermine its oxygen content. Air is added to the other part, and themixture of air and sample gas is conveyed to the combustible nalyzingchamber to be analyzed to determine its combustible content. Anelectrically heated catalytic combustion Wire, suspended in each of theanalyzing chambers, ignites the gaseous mixture passing through thechamber; and the resulting heat of combustion increases the resistanceof the catalyst wire proportionally to the amount of oxygen orcombustibles in the gaseous mixture. The catalyst wire in each analyzerforms a leg of a Wheatstone bridge circuit, and the increased resistanceof each catalyst wire is measured directly in percentage of oxygen orcombustibles on a millivoltmeter connected across each Wh'eatstonebridge circuit.

In analyzing a gas for its oxygen content, the apparatus may be designedto operate in any of two percentage ranges. The ranges selected for thepreferred form are: to 4% oxygenlow range, and 0% to 20% oxygen-highrange. To operate the analyzer in the low range, the apparatus isadjusted in such a way that the volume of hydrogen added to the gas isdecreased to approximately one-fifth the volume added when operating inthe high range; and the amount of the mixture of gas and hydrogen burnedby the catalyst wire is approximately five times that amount burned whenoperating in the high range. These adjustments are accomplished by theoperation of a multipole switch, which is electrically connected to anelectrolytic hydrogen generator, and mechanically connected to a bafiielocated in the combustion chamber. By turning the switch to the lowrange position, a resistance is connected into the electrolytic hydrogengenerator circuit order to decrease the generation of hydrogen, and thebafiie in the combustion chamber is moved out of the path of flow of thegas mixture to the catalyst wire, such that more gas mixture will beignited by the catalyst wire. By these adjustments, the catalyst wirewill operate in the same temperature range for both the high and lowpercentage ranges.

In analyzing a. gas for its combustible content, the apparatus may bedesignedto operate in any of two percentage ranges. The ranges selectedfor the preferred form are, 0% to 4% combustibles-low range, and 0% to20% combustibleshigh range. When operating the analyzer in the lowrange, the apparatus is adjusted such that a mixture of live partssample gas and one part air is ignited by the catalyst wire. Whenoperating in the high range, the apparatus is adjusted such that amixture of one part sample gas and five parts air is ignited by thecatalyst wire. The adjustment of the mixture ratio is performed by useof a switch which is mechanically connected to a movable valve in theproportioning pump. The proportioning pump has two suction ports, one ofwhich draws in five volumes of gas while the other port draws in onevolume of gas. When the switch is turned to the low range position, themovable valve is adjusted to connect the five volume suction port to thesample gas inlet, and the one volume suction port to the air inlet. Inthe high ringe position, the five volume suction port is connected tothe air inlet and the single volume suction port is connected to thesample gas inlet. The catalyst wire will operate in the same temperaturerange for both the high range and low range analysis positions.

The invention which has been broadly explained will now be specificallydescribed in connection with the accompanying drawing, which illustratesa flow and wiring diagram of the preferred form of the invention.

Referring to the drawing, a continuous sample of the gas to be analyzedis withdrawn from pipe I, which pipe may be the stack of a furnace orthe exhaust pipe of a combustion engine. This sample is conveyed throughconduit 2 to a gas filter 3, where suspended liquid and solid material,such as water and dust, are removed from the gas by a cotton filtercontained therein.

This cleaned and dried gas sample is conducted through conduit 4 to avalve 5. With valve 5 in the position illustrated, the gas passesthrough passage 0 into conduit 1, through which it passe" to suctionport 8 of the rotary sliding vane pump 9.

The pump 9 rotates at a constant speed in a counterclockwise direction,having one suction port 8, and two discharge ports to and M. Thefunction of pump 8 is to discharge a constant flow of gas at port llregardless of variation in the pressure of the gas entering the pump.

This is accomplished by the use of the atmospheric discharge port iii,which is located a little more than 45 in the direction of rotation pastthe point of maximum clearance between the rotor and the innerperipheral surface of the pump housing. As the gas passes thisatmospheric discharge port ill at varying pressure, it is brought toatmospheric pressure, and any gas in excess passes out through thepassage of port l0. The gas is compressed between the atmosphericdischarge port I0 and the sample discharge port II, such that a constantuniform flow of gas is exhausted from the pump into conduit !2,regardless of any variation in the pressure of the gas entering the pump9 at suction port 8.

The sample gas pumped into conduit i2 is conveyed therein to aperture Mof oxygen analyzing chamber [3. The sample gas is analyzed in chamber l3for its oxygen content by igniting a mixture of sample gas withhydrogen. The amount of hydrogen added to the sample gas is in slightexcess of the amount of hydrogen required to react with the oxygen of agas sample.

The hydrogen for the oxygen analysis is gen-- erated at a constant rateby an electrolytic hydrogen generator l5, which generator has an anodeI6 separated from a cathode i? by an asbestos diaphragm l8; all of saidparts being immersed in an electrolytic solution, such as a solution ofsodium hydroxide. The hydrogen generated at cathode I! passes throughconduit I9 to valve 5, through which it flows by means of a peripheralgroove 20 into a conduit 2!. The hydrogen flowing through conduit 2|enters conduit l2, mixes with the sample gas flowing therein, and themixture enters aperture I4 of the oxygen analyzing chamber I3.

In the oxygen analyzing chamber IS a catalytic ignition wire 22 issupported on one of the posts 23, which posts are surrounded by animpervious metallic cylindrical shield 24. A movable baflle 25 issupported over the shield 24, said baffle 25 having a central bore 26,and four openings 21 leading to the bore 26 from the side of the bafile.

The mixture of sample gas and hydrogen entering the oxygen analyzingchamber I 3 by the aperture 14, passes upwardly around the outside ofthe impervious shield 24. With the baflie 25 in the positionillustrated, part of the mixture of sample gas and hydrogen passes intothe shield 24 by diffusion and convection currents to be ignited by thecatalyst wire 22 contained therein.

The remainder of the gas-hydrogen mixture along with the products ofcombustion pass upwardly out of the oxygen analyzing chamber |3 by wayof the bore 26 of the baffle 25.

If the baflle is lowered to rest on the top of the shield 24, theair-hydrogen mixture after entering the oxygen analyzing chamber l3passes through the side openings 21 into the bafile 25 and down throughthe bore 26 into the shield 24. Much less gas mixture enters shield 24to be ignited by catalyst wire 22 when baffle 25 is lowered on shield24. The area of accessibility of the gas to enter shield 24 by way ofthe bore 26 is much less than the area of accessibility of the gas toenter the shield unobstructed by baflle 25.

The mixture of hydrogen and sample gas is burned on the surface of thecatalyst wire 22 which is electrically heated. The combustion of themixture will generate more or less heat in accordance with the amount ofoxygen present in the gas sample. This heat varies the resistance of thecatalyst wire 22, and a measure of this resistance is used fordetermining quantitatively the amount of oxygen in the sample. Thecatalyst wire 22 forms one leg of a Wheatstone bridge, which bridge isused for measuring the resistance of the catalyst wire 22. A directcurrent is used in the Wheatstone bridge, and in the electrolytichydrogen generator l5. All of the electrical current used in theapparatus is derived from a single source.

An electric current is introduced into the wires 28 from a power source,the current being controlled by a switch 29. The current is conducted bywires 23 to transformer 30, where the voltage is reduced toapproximately twelve volts. The secondary transformer current isconducted by Wires 3| to full wave rectifier 32, which has a ballastlamp 33, such as an amperite, in series with the circuit.

A rectified D. C. current, leaving rectifier 32 at approximately 8 voltsis conducted by line 34 to a Wheatstone bridge 35, then through thebridge 35 to a Wheatstone bridge 36. The current leaves bridge 36through line 31, passing through a 0.2 ohm resistance 38, and thencethrough line 39 to the cathode ll of hydrogen generator l5. The currentpassing through the electrolytic solution of the hydrogen generator l5leaves the generator at anode l6, and is conducted by line 40 back torectifier 32.

The Wheatstone bridge 35 is employed in determining the oxygen contentof the gas. One of its legs is the catalytic wire 22, which ignites themixture of sample gas and hydrogen in the combustion chamber l3. Whenthe gas burns, it heats the catalyst wire, increasing its resistance,and thus unbalancing the bridge. A millivoltmeter 4| is connected acrossthe bridge 35, and any unbalancing of the bridge 36 causes a current toflow to the millivoltmeter 4|, through the multipole switch 42. Themultipole switch 42 is used in connection with the analyzer for thepurpose of selecting the range of operation of the analyzer. There aretwo percentage ranges: 0 to 4% oxygen or low range, and 0 to 20% oxygenor high range.

The switch 42 is a triple-pole, triple-throw switch, having a movableshaft 43 with an adjusting lever 44 at one end and a cam 45 at the otherend. Three contact blades 46, 41 and 48 are fixed on the shaft 43, andarranged for each blade to connect two contact points at each positionof the switch. Several of the contact points are internally connectedtogether; thus contact point 49 is connected to contact point 50,contact points 5|, 52 and 53 are connected together; contact points 54,55 and 56 are connected together; contact point 5! is connected tocontact point 58; and contact points 59, 60 and 6| are connectedtogether. The cam 45 connected to the switch shaft 43, when turned,raises and lowers the baffle 25 in the oxygen analyzing chamber |3 bymeans of linkage 61.

The Wheatston bridge 36 shown in the illustration is composed of anactive catalytic platinum-alloy wire 22, a wire 69 of the same materialand having substantially the same resistance, and two gold platedplatinum-alloy inactive wires 68 and Ti], each of which has the sameresistance. The catalyst wire 22 and one of the gold plated wires 68 aremounted upon the posts 23 in. the oxygen analyzing chamber l3, and whenair alone is passeed through chamber I3, the bridge 33 should bebalanced with no current flowing through the millivoltmeter 4| connectedacross the bridge 35.

When a gas sample mixed with hydrogen is passed through combustionchamber l3, it will be ignited by catalyst Wire 22, whose resistancewill be increased due to the temperature rise. The increase inresistance will unbalance the bridge 36 and a current will flow to themillivoltmeter 4!. With the multipole switch 42 in the low-rangeposition, as illustrated, the meter current flows through line H tocontact point 49, thence through the internal connections and switchblade 46 of the switch 42, and out of the switch at contact point 5|, toflow through line 12 to the meter 4|. The current leaves the meter 4| toflow through the line 13 to contact point 54, then through theconnections and switch blade 41 of switch 42, leaving at contact point64 through line H to Wheatstone bridge 33. A resistance 15 is placed inthe line 74 for the purpose of calibrating the meter to give directreadings on its scale in percentage oxygen of the gas being analyzed.

Since the amount of hydrogen added to the sample gas is decreased duringthe operation of the analyzer in the low-range, a resistance 16 isplaced in parallel with the hydrogen generator Hi. The circuit of thehydrogen generator, the rectifier, and the bridges for low-rangeoperation may be described as follows: rectified D. C. current leavesrectifier 32 by line 34, passes through bridge 35, through bridge 35,leaving by line 31, then through the 0.2 ohm resistance 38. G ne part ofthe current goes to hydrogen genorator 15 by line 39, then to therectifier 32 by line 40; the other part of the current goes by line H tocontact point 6 i, then through the internal connections and switchblade 48 of switch 42, out at contact point 58, and thence through line18, through the 1.3 ohm adjusted resistance 16 to the rectifier 32.

When analyzing a gas having more than 4% oxygen, the switch 42 is turnedcounterclockwise, from the position of the switch illustrated. Byturning the switch 42 to this high-range position, the flow of hydrogenfrom the generator I5 is increased, and the flow of sample gas andhydrogen mixture to the catalyst wire 22 is decreased.

By thus turning the switch 42, 90 counterclockwise, the cam 45 lowersthe baffle 25 down upon the shield and as a result, the gas and hydrogenmixture will have to enter the baffle 25 through side holes 21, and godown through bore 26 to be burned by catalyst wire 22. The

- tact point 66.

central bore 23 is designed to permit approximately only one-fifth asmuch gas and hydrogen mixture to reach the catalyst wire 22 when thebaiile is lowered, as will reach the wire when the baffie is raised.

The circuit for the rectifier, the bridges and the hydrogen cell for thehigh range position of the switch may be outlined as follows: thecurrent leaves rectifier 32 by line 34, goes through bridge 35, throughbridge 36, through line 31, to con- The current goes through switchblade 48 and the internal connections of the switch 42, out of theswitch at point 3|, through line I1, through line 39, thus cutting outboth the 0.2 ohm resistance 38, and the 1.3 ohm resistance I6. Thecurrent then flows through line 39, goes through the hydrogen cell I outthrough line 49 back to the rectifier 32. By cutting out resistance 38and 19 the generation of hydrogen will be increased approximately fivetimes.

If a gas is passed through the analyzer when switch 42 is in thehigh-range position, the meter current flow from the bridge 36 to themillivoltmeter 4|, due to unbalancing of the bridge, will go throughline II to contact point 49. This current flows through the switch blade46 to contact point 5|, and out through line 12 to the millivoltmeter4|. The current leaves the millivoltmeter 4| by line I3, going tocontact point 54, through blade 41 to contact point 63. The currentleaves the contact point 63 through line 8! to return to bridge 35. Thecurrent passes through high-range calibrating resistance 79, in the line8|. The calibrating resistance I9 is used in order that a direct readingof the percentage of oxygen in the gas to be analyzed can be readdirectly on a meter scale of the millivcltmeter 4|.

By turning the switch 90 clockwise from the position illustrated theapparatus will be adjusted to give temperature readings on themillivoltmeter 4! of the temperature of the gas withdrawn from the pipeI. The temperaure of the sample gas is important when the apparatus isused in conjunction with adiusting furnaces for their maximum operatingefiiciency. A thermocouple 82 is inserted in pipe I near the opening ofconduit 2. A lead 83 is connected to contact point 65, and a lead 84 isconnected to contact point 62.

When the switch 42 is in position for measuring the gas temperature, thecurrent of the thermocouple goes through line 83 to contact point 55.through switch blade 41 and the switch connections, and out throughcontact point 54 through line 13 to the millivoltmeter 4|. The currentleaves the millivoltmeter 4| through line 12 going to contact point 5|,then through switch blade 46 and the switch connections and out throughcontact point 62, through lead 84 to thermocouple 82.

The millivoltmeter 4| has three scales upon its face; a high-rangepercentage oxygen scale; a low-range percentage oxygen scale; and atemperature scale.

Part of the sample gas is mixed with air, ignited by a catalyst wire ofa Wheatstone bridge, and the percentage of combustibles in the gas isdirectly indicated on a millivoltmeter connected across the Wheatstonebridge. The source of the sample gas is from the atmospheric dischargeport ID of the sample pump 9. The sample gas discharged at port I0 is atatmospheric pressure, and part is drawn through the pump passage 85 ofthe sample pump 9 to a range changing valve 86 located in pump 81.

The pump 8i is a proportional mixing pump which has two suction ports 88and 89, and one discharge port 99. The suction ports are so located withrespect to the periphery of the housing, that suction port 88 draws infive volumes of a gas while suction port 89 draws in only one volume ofgas. The ports have passages leading to the seat of the movable valve86, and the openings in the valve seat are 90 apart on the periphery.

The range changing valve 88 has two axial passageways leading from theends of the valve, one of which, passage 9|, is open to the air and theother, passage 92, opens into passage of pump 9. With the valve 86 inthe valve seat of the pump 3? in the position illustrated, sample gasfrom passage 85 will be drawn through valve passage 92 to port 83 by wayof the port passage. Air will be drawn through valve passage 9| to port89 through the port passage. The mixture discharged at port 30 willconsist of five parts sample gas and one part air.

If the valve 86 is turned clockwise from the position illustrated, thenthe sample gas from passage 85 is drawn through valve passage 9| intoport 89, and air is drawn through valve passage 9| to port 88, such thatthe mixture discharged through port 98 is one part sample gas and fiveparts air.

The mixture of air and sample gas discharged at a constant rate at port99, passes through conduit 93 to the aperture 94 of a combustibleanalyzing chamber 95. The combustible analyzing chamber 95 isconstructed similarly to the oxygen analyzing chamber I3 except it hasno bafile. A catalyst wire 96 is mounted on one of the posts 91 whichare enclosed in an impervious cylindrica1 shield 93. The gas mixtureentering the aperture 94 passes upwardly around the outside of theshield 98, part of which passes down into the shield 98 by diffusion andconvection currents to be ignited by the catalyst wire 96. The remainderof the gas mixture, along with the products of combustion of the part ofgas mixture ignited, pass out of analyzing chamber 95 by means of a hole93 in the top of said chamber.

The catalyst wire 96 forms one leg of the Wheatstone bridge 35, throughwhich passes the rectified D, C. current from rectifier 32 as previouslydescribed. When gas is passed through the analyzing chamber 95, andignited by the catalyst wire 95, the temperature of the wire is raised,thus increasing its resistance. The change in resistance of one leg ofbridge 35 unbalances the bridge causing a current to flow through switchIill to millivoltmeter I90 connected across the bridge 35.

The apparatus is designed to analyze gases in two different percentagesof combustible ranges: 0 to 4% combustibles or low range, and 0 to 20%combustibles or high range. The switch IIJI is used for selecting therange of operation of the analyzer.

The switch I9I is a single-pole, double-throw switch having a shaft I82with an adjusting lever I03 at one end and a disk I04 at the other end.The movable valve 86 is connected to disk I04 by the linkage I05, suchthat the valve 86 will move in the same direction as the lever I83.There are four contact points on the switch IUI, of which contact pointsI06 and I01 are connected together by connections in the 9. switch. Acontact blade III is attached to the shaft I02, which blade connectscontact point I06 to contact point I08 when the blade is in a verticalposition, and connects contact point IN to contact point I09 when theblade is in a horizontal position.

The Wheatstone bridge 35 is composed of the platinum alloy catalyst wire56, a wire of similar material III and of approximately the sameresistance, and two nickel plated platinum-alloy wires H and H2, ofequal resistance. The catalyst wire 90, along with the nickel platedwire H0 is mounted on posts 01 in the combustible analyzing chamber 95,

When the bridge 35 is in an unbalanced condition and the switch IOI isin the low-range position, as illustrated, meter current leaves thebridge 35 by the line I I3, and flows to the millivoltmeter I00. Thiscurrent leaves the meter I00 by line 4, going to contact point [01,passing through the switch IOI, out at contact point I08 through line II5 to the bridge 35. The low-range calibrating resistance H6 is placedin the line II5 i" order that direct readings of the percentagecombustibles of the gas analyzed are indicated on a scale ofmillivoltmeter I00.

With the switch IOI in' the low-range position, the disk I04 holds themovable valve 85 in the position illustrated, such that five volumes ofsample gas enter port 88 of the pump. 81, and one volume of air entersthe port 89.

To operate the apparatus in the high-range, the switch IN is turned 90clockwise from the position illustrated, and meter current will flowfrom the bridge 35, due to its unbalanced condition,

through line II3 to millivoltmeter I00. The current leavesmillivoltmeter I00 through line H4, going to contact point I01, passingthrough switch blade Ill to contact point I09, and returning to bridge35 by line H8. The high-range calibrating resistance I I9 is placed inthe line I IS in order that direct readings of the percentagecombustibles may be read from a scale of meter I00.

When the switch IOI is turned to the high range position, the movablevalve 85 is also turned 90 clockwise from the position illustrated. Inthis position of the valve 86, one volume of sample gas is drawn intoport 89 and five volumes of air are drawn into port 38 of pump 81, suchthat the air-gas mixture entering the analyzing chamber 95 in thehigh-range position will be in the ratio of five parts air to one partgas.

The millivoltmeter I00 has two scales upon its face: a high-rangepercentage combustible scale and a low-range percentage combustiblescale.

nected directly across the power intake leads 28 This motor is aconstant speed motor, and drives the interconnected pumps 9 and 81 at aconstant rate so that the pumps operate to deliver a predeterminedquantity of gas mixture for analysis at a uniform flow.

In order to obtain accurate analyses, the apparatus should beperiodically checked to balance Wheatstone bridges 35 and 36, and to setthe flow of hydrogen delivered by the hydrogen generator I5 to theoxygen analyzer. The valve 5 is adapted to be used in conjunction withother controls for making these adjustments, as the valve 5 controls thetype of gas going to the sample pump 9 and connects the flow of hydrogento the oxygen analyzing chamber l3.

The valve 5 can be turned to four different positions. The positionillustrated being the read or sample gas analysis position; by

10 turning the valve 60 counterclockwise, it is in the check ratio ofhydrogen to sample gas position; by turning the valve counterclockwise,it is in the check balance of Wheatstone bridges" position; and byturning the valve counterclockwise, it is in the "011 position.

The valve is turned to the off position when the apparatus is not inuse. The upper section of the valve 5 shuts off any sample gas flow tothe pump, and the lower section of the valve 5 connects the hydrogengenerator I5 to the oxygen analyzing chamber I3.

When the valve 5 is turned to the check balance of Wheatstone bridgesposition, air alone is pumped through both analyzing chambers in orderthat the bridges can be electrically balanced by potentiometers I20 andI2I. When an electrical balance is reached, the millivoltmetersconnected across the bridges should have a zero reading. In thisposition the upper section of valve 5 connects air inlet I22 throughvalve passage 8 to the tube 1 leading to sample pump 0. The lowersection of the valve 5 shuts off the flow of hydrogen to the oxygenanalyzing chamber I3 and vents the hydrogen through slot I25 of thevalve 5 to a valve vent I23. A potentiometer I26 connected acrossWheatstone bridge 35 is adjusted to balance the bridge 35, and apotentiometer I2i connected across the Wheatstone bridge 38 is adjustedto balance the bridge 36.

When valve 5 is in the check ratio of hydrogen to sample gas position,air is pumped to both analyzers and hydrogen is supplied to oxygenanalyzing chamber I3. In this position of valve 5, its upper sectionconnects the air inlet I22 to the conduit I by valve passage 6, thusintroducing air into the suction of the pump 9. The lower section ofvalve 5 connects hydrogen generator I5 to oxygen analyzing chamber I3.The ratio of hydrogen to sample gas in the gas mixture entering theoxygen analyzing chamber should be such that there is a slight excess ofhydrogen over the amount needed to react with the maximum amount ofoxygen encountered in either the high range or the low range. When theswitch 42 is in the high-range position with the sample gas being air,the correct ratio of hydrogen to sample gas is obtained by adjusting thevent I26 until a maximum reading is indi cated on the high-range scaleof millivoltmeter 4i connected across bridge 36. When the switch is inthe low-range position and the sample gas pumped to the analyzer is air,the correct ratio oi hydrogen to sample gas is obtained by adjusting 3.1the variable resistor I5 until a reading slightly in A motor I24 foroperating the pumps is conexcess of 4% is obtained on the low-rangescale of millivoltmeter 4I connected across bridge 35.

When the valve 5 is in the read position as illustrated, the sample gasis analyzed for its oxygen content in the oxygen analyzing chamber andits combustible content in the combustible analyzing chamber. The uppersection of valve I2 connects the gas passage conduit 4 to the pumpsuction passage conduit I by the groove 6, and the lower section ofvalve 6 continues to introduce hydrogen from the hydrogen generator I5to the oxygen analyzer I3.

The preferred form of the invention having been thus described, What isclaimed as new is:

l. A gas analyzer for quantitatively measuring the oxygen content of agas, comprising a combustion chamber, means for passing a continuousstream of gas to be analyzed at a uniform rate through the chamber, ametal shield mounted centrally within the chamber having imperforatebase and side walls positioned in baffling relation to the stream of gasflowing through said chamber, a Wheatstone bridge electric circuitembodying a catalyst wire leg mounted within said shield and agalvanometer for measuring variations in electric conductivity of thecatalyst, an apertured movably mounted closure for the top of the metalshield, and a switching mechanism controlling the galvanometer circuitfor adjusting the sensitivity of the galvanometer, said switchingmechanism and closure moving means being interconnected and arranged forsimultaneous adjustment of the position of said closure and thesensitivity of said galvanometer.

2. In a multi-range gas analyzer adapted for analyzing gasquantitatively for a constituent of a gaseous mixture, a combustionchamber, means for positively delivering a continuous flowing stream ofgas to be analyzed through a conduit to said chamber, means comprising aWheatstone Bridge electric circuit including a catalyst wire leg mountedin said chamber for setting up combustion therein and a galvanometer formeasuring any increase in temperature thereby developed, means connectedwith said conduit for supplying to the gas stream a continuous flowingstream of gas which is combustively reactant with said constituent ofthe gas, means connected with the supplying means for changing therelative volumes of gas and reactant gas in the mixture, and anelectrical switching mechanism controlling the galvanometer circuit foradjusting the sensitivity of the galvanometer, said volume changingmeans and switching mechanism being connected together and so arrangedthat adjustment of the switching mechanism to actuate said sensitivityadjusting mechanism will simultaneously operate said volume changingmeans.

3. In a multi-range gas analyzer adapted for analyzing products ofcombustion quantitatively for oxygen content, a combustion chamber,means for delivering to said chamber a continuous flowing stream of thegas to be analyzed, a Wheatstone bridge electric circuit including acatalyst wire leg mounted in said chamber for setting up combustiontherein, a galvanometer for measuring any increase in temperaturethereby developed, an electrolytic hydrogen cell and connectionsarranged for adding to the gas stream flowing to the combustion chambera continuously flowing stream of hydrogen, and means in the bridgecircuit including electrical switches and calibrated resistances wherebyto adjust the sensitivity of the galvanometer and the rate of supply ofhydrogen by the hydrogen cell, said switches and the circuits of saidresistances being interconnected and arranged for simultaneouslyactuating said sensitivity adjusting means and said hydrogenproportioning means for making analyses in different ranges.

ALAN P. SULLIVAN.

